This thesis develops Extensible Dependency Grammar (XDG), a new
grammar formalism combining dependency grammar, model-theoretic
syntax, and Jackendoff's parallel grammar architecture. The design of
XDG is strongly geared towards modularity: grammars can be modularly
extended by any linguistic aspect such as grammatical functions, word
order, predicate-argument structure, scope, information structure and
prosody, where each aspect is modeled largely independently on a
separate dimension. The intersective demands of the dimensions make
many complex linguistic phenomena such as extraction in syntax,
scope ambiguities in the semantics, and control and raising in the
syntax-semantics interface simply fall out as by-products without
further stipulation.
This thesis makes three main contributions:
1. The first formalization of XDG as a multigraph description
language in higher order logic, and investigations of its
expressivity and computational complexity.
2. The first implementation of XDG, the XDG Development Kit (XDK),
an extensive grammar development environment built around a
constraint parser for XDG.
3. The first application of XDG to natural language, modularly
modeling a fragment of English.